The present invention relates to a fluid dispenser device, and more particularly to an inhalation device including a metering valve, the device being of the “Metered Dose Inhaler” (MDI) type, in which actuation of the metering valve is controlled by the user inhaling.
Such inhalation-actuated MDI inhalers, generally referred to as “Breath-Actuated Inhalers” (BAI) using metering valve systems are usually based on a trigger mechanism including a spring, said spring being released by an appropriate device when the user inhales. The spring is usually loaded or compressed by actuating a lever, e.g. while opening the lid of the inhaler mouthpiece, and the force of the spring is directed, at the time of inhalation, against the metering valve of the inhaler, or against the reservoir, enabling the valve to be actuated by displacing the valve member relative to the reservoir. This is made possible as a result of that one of the elements from amongst the valve member and the reservoir, that is not subjected to the action of the previously loaded spring, being held stationary inside the device. Once the metering valve has been actuated, and once the fluid contained in the reservoir has been dispensed, said metering valve generally remains compressed, with the valve member in its actuated position, until the load from the spring is relaxed, which can only occur when the lid of the mouthpiece is closed.
The above-described structure is the source of a problem which is linked to the way in which most metering valves operate. The valves generally include a return spring, and a metering chamber which is filled by the mixture constituted by fluid, generally a medicine, and a liquefied propellant gas. The metering chamber is filled by gravity, and only when the valve member is displaced from its dispensing position to its rest position, i.e. when the force applied on the valve by the spring of the trigger system is relaxed. This therefore implies that the tension of the spring must be released when the device is in a position that is appropriate to enable the metering chamber of the valve to be filled by gravity. The position required for the metering chamber to be filled effectively and completely is the working position of the inhaler, in which the reservoir is generally disposed above the metering valve, the user having the mouthpiece in the mouth so as to breath in the dose of dispensed fluid.
Once the dose of fluid has been dispensed, when the user removes the device from the mouth, there is a high probability that the inhaler is no longer in the position required for effective filling, and there is a high risk of the user closing the lid of the mouthpiece while the inhalation device is in an inappropriate position for filling the metering chamber completely.
Systems have therefore been proposed for releasing the valve member, and enabling it to be returned automatically to its rest position, independently of any intervention by the user. Such systems generally include means that are actuated when the valve member reaches its dispensing position, and which enable the valve member to return immediately to its rest position, and therefore enable the metering chamber to be filled in the appropriate position. Document U.S. Pat. No. 5,826,571 discloses such a system.
The use of such valve-member release systems can however lead to other drawbacks.
It is necessary to allocate enough time to enable the entire dose to be expelled from the metering chamber during actuation. Unfortunately, in general, the fluid is dispensed when the inlet orifice of the valve member is inside the metering chamber. This takes place at the end of the actuating stroke of the valve member and at the start of its return stroke towards its rest position. Thus, the valve-member release systems, which return said valve member to its rest position as soon as it has reached its dispensing position, risk reducing the time taken to empty the metering chamber to too great an extent. In other words, the valve member risks being released and returned to its rest position before the entire dose has been dispensed. The accuracy of dose metering can be affected thereby, which can have very serious consequences, in particular with certain pharmaceuticals whose effectiveness is linked directly to the accuracy with which the doses are dispensed. Document WO 01/70319 discloses a device including means for temporarily blocking the valve member in the dispensing position. The system presents the drawback of keeping the valve open during said temporary blocking, thereby presenting a risk if the user moves the device before the valve closes.